Elongate hollow machine parts are increasingly constructed from non-metal materials, such as composite materials. Typically, such composite materials are constructed by a heat curing process.
In such heat curing processes, it is typical to form the machine parts by applying heat curable material to the exterior of a mandrel, curing the non-metal material, cooling the cured non-metal material—while the part remains supported by the mandrel—and, finally, removing the finished part from the mandrel.
A problem arises when the part is to have a lateral projection, such as a flange. Since mandrels are typically made from steel, and therefore have a much larger coefficient of thermal expansion than the non-metal material. The mandrel, including the lateral member on the mandrel used to support the lateral projection, expands at a greater rate than the composite part. This causes a gap to form between the lateral portion (on the composite part) and the lateral member (on the mandrel), thereby resulting in a reduction of supporting pressure between the lateral projection and the lateral member. This, in turn, may cause the lateral projection of the non-metal part to prematurely disengage from the support provided by the lateral member. Such premature disengagement frequently leads to porosity, delaminations and/or other laminate quality problems in the non-metal part.
Another problem which arises when a composite part is to have a lateral projection is that the lateral member on the mandrel can crush the lateral projections during cool-down.
In an attempt to deal with these problems, some prior art mandrels have been designed with “floating” lateral members—lateral members free to slide along the exterior of the central portion of the mandrel. While such floating lateral members generally succeed in solving the tendency of the lateral members to crush the lateral projections during cool-down, the final disposition of the lateral members cannot be accurately controlled. This means that the location of the lateral projections on the composite part cannot be accurately controlled.
Accordingly, there is a need for a mandrel capable of forming a machine part having a lateral projection which avoids the aforementioned problems in the prior art.